Date: Wed, 04 Apr 2012 08:03:11 -0700 From: perryh@pluto.rain.com To: illoai@gmail.com Cc: questions@freebsd.org Subject: Re: current pids per tty Message-ID: <4f7c62af.TE2lRux2ew4%2BbRu8%perryh@pluto.rain.com> In-Reply-To: <CAHHBGkqw865mGPS-9PSBfFa9qOJO8wJcrsTvfr4aoxw%2B0EF9Eg@mail.gmail.com> References: <CAPkyVLzPuX3jxRRRVsJEtcYE%2B4kAaas50RuzbVByEUixuHhQdA@mail.gmail.com> <CAHHBGkqw865mGPS-9PSBfFa9qOJO8wJcrsTvfr4aoxw%2B0EF9Eg@mail.gmail.com>
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"illoai@gmail.com" <illoai@gmail.com> wrote:
> (there is an executable named /usr/bin/jobs, but . . .
> well run "cat /usr/bin/jobs" & see for yourself).
Whoa! Does /usr/bin/jobs even work?
$ cat /usr/bin/jobs
#!/bin/sh
# $FreeBSD: src/usr.bin/alias/generic.sh,v 1.2.10.1.4.1 2010/06/14 02:09:06 kensmith Exp $
# This file is in the public domain.
builtin ${0##*/} ${1+"$@"}
It looks as if generic.sh intends to have the same effect as the
builtin matching the name under which the script is run, but at
least for "jobs" I don't think it will DTRT because it will run
in the wrong context:
* The builtin "jobs" command will report all background jobs known
to the shell in which it is issued.
* Because it is a shebang script, running /usr/bin/jobs will cause
the shell in which it is run to fork/exec an instance of /bin/sh,
and that instance will execute the /usr/bin/jobs script, thus it
will will be the new /bin/sh instance that executes _its_ builtin
"jobs" command -- reporting nothing, since _that_ instance has not
put anything into the background (and has no knowledge of what-all
its parent shell may have put in the background).
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